The Collaborative International Dictionary of English v.0.48:

Checkmate \Check"mate\ (-m[=a]t), v. t. [imp. & p. p.
   Checkmated; p. pr. & vb. n. Checkmating.]
   1. (Chess) To check (an adversary's king) in such a manner
      that escape in impossible; to defeat (an adversary) by
      putting his king in check from which there is no escape.
      [1913 Webster]

   2. To defeat completely; to terminate; to thwart.
      [1913 Webster]

            To checkmate and control my just demands. --Ford.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Checkmate \Check"mate\ (ch[e^]k"m[=a]t), n. [F. ['e]chec et mat,
   fr. Per. sh[=a]h m[=a]t checkmate, lit., the king is dead,
   fr. Ar. m[=a]ta he died, is dead. The king, when made
   prisoner, or checkmated, is assumed to be dead, and the game
   is finished. See Chess.]
   1. The position in the game of chess when a king is in check
      and cannot be released, -- which ends the game.
      [1913 Webster]

   2. A complete check; utter defeat or overthrow.
      [1913 Webster]

WordNet (r) 3.0 (2006):

checkmate
    n 1: complete victory
    2: a chess move constituting an inescapable and indefensible
       attack on the opponent's king [syn: checkmate, mate]
    v 1: place an opponent's king under an attack from which it
         cannot escape and thus ending the game; "Kasparov
         checkmated his opponent after only a few moves" [syn:
         checkmate, mate]

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "checkmate":
   arrest, baffle, bafflement, balk, balking, bell, blast, block,
   brake, brave, bring to, bring up short, challenge, check,
   circumvent, confound, confounding, confront, confusion, contravene,
   counter, counteract, countermand, counterwork, cross, cut short,
   cutoff, dam, dash, dead stop, deadlock, defeat, defy, destroy,
   discomfit, discomfiture, disconcert, disconcertion, discountenance,
   dish, disrupt, draw rein, elude, end, endgame, ending,
   final whistle, flummox, foil, foiling, freeze, frustrate,
   frustration, full stop, grinding halt, gun, halt, knock the chocks,
   lockout, nonplus, perplex, pull up, put paid to, rebuff, repulse,
   reversal, reverse, rout, ruin, sabotage, scotch, setback,
   sit-down strike, spike, spoil, stalemate, stall, stand, standoff,
   standstill, stay, stem, stem the tide, stonewall, stop, stop cold,
   stop dead, stop short, stoppage, strike, stump, thwart, thwarting,
   upset, walkout, work stoppage